<template>
  <div class="Child">
    <h3>我是Child组件</h3>
    {{sum}}
  </div>
</template>

<script>
import {ref} from 'vue'
export default {
  name: "App",
  async setup() {
    let sum = ref(0)
    let p = new Promise((resolve,reject)=>{
      setTimeout(()=>{
        resolve({sum})
      },3000)
    })
    return await p
  }
};
</script>
 <style>
 .Child{
   background-color: skyblue;
   padding: 10px;
 }
 </style>